Distribution and grain size of sand in the Miocene wave-dominated Billund delta, Denmark

Erik S Rasmussen,Jens Bruun-Petersen

doi:10.34194/geusb.v20.4891

Abstract

The distribution of sand in deltas depends on the delta regime: wave, fluvial or tidal-dominated delta (Orton & Reading 1993; Bhattacharya & Giosan 2003). During the Early Miocene, three delta complexes built out from the Fennoscandian Shield into the eastern North Sea Basin (Rasmussen 2004). The oldest delta complex, which is informally named the Billund delta, is located in Jylland (Fig. 1). This delta complex was mainly wave-dominated (Rasmussen & Dybkjær 2005; Hansen & Rasmussen 2008; Rasmussen 2009a). Recently, it has been demonstrated that in modern wave-dominated delta environments sand mostly accumulates on the updrift portion of the delta (Fig. 2) whereas alternating mud and sand, e.g. barrier-lagoon complexes, occupy the downdrift portion of the delta system (Bhattacharya & Giosan 2003). The current study shows that most of the sand in the submarine part of the Miocene wave-dominated Billund delta (mainly lower shoreface and delta slope sand) was deposited downdrift to the delta front and thus differs from the foreshore and uppermost shoreface accumulation found in recent delta complexes.

Highlights

The distribution of sand in deltas depends on the delta regime: wave, fluvial or tidal-dominated delta (Orton & Reading 1993; Bhattacharya & Giosan 2003)
The aim of this study is to map the distribution of submarine delta sand in the Billund delta complex
The eastern North Sea Basin was subject to inversion in the Early Miocene (Rasmussen 2009b)

Summary

Geological setting

The eastern North Sea Basin was subject to inversion in the Early Miocene (Rasmussen 2009b). The inversion tectonism resulted in high sediment input into the Norwegian–Danish Basin and progradation of delta complexes. During the Early Miocene, the deltas built far out into the basin (Rasmussen 2004) and were predominantly wave-dominated (Rasmussen & Dybkjær 2005; Fig. 1). In the Early Miocene, a warm temperate to subtropical, humid climate prevailed (Larsson-Lindgreen 2009). During the Miocene and Pliocene, the region was located in the northern part of the zone of prevailing westerly winds, which led to a high wave energy regime in the eastern part of the North Sea Basin due to the long fetch across the North Sea (Galloway 2002; Rasmussen et al 2008)

Sand distribution in the Billund delta

Depositional environment

Failure due to instability of slope after a flood

Discussion